Composition-controlled polymers, methods of formation, and uses thereof

ABSTRACT

A composition of matter includes a mixture of styrene derivative monomers and methacrylate/acrylate derivative monomers, which form hydrogen bonds between/among different precursors, and initiators, and the compositions are used to achieve composition control of the forming polymer, with the mole fraction of acrylate/methacrylate and styrene moieties in the forming polymer determined preferably by the monomer reactivity and monomer composition rather than the viscosity of the monomers.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 15/276,821, filed Sep. 27, 2016, and entitled RAPID AZEOTROPIC PHOTO-COPOLYMERIZATION OF STYRENE AND METHACRYLATE DERIVATIVES AND USES THEREOF, which claims the benefit of provisional patent application 62/234,088 filed Sep. 29, 2015 and entitled RAPID AZEOTROPIC PHOTO-COPOLYMERIZATION OF STYRENE AND METHACRYALTE DERIVATIVES FOR DENTAL APPLICATIONS. The disclosures of these two applications are hereby incorporated by reference.

BACKGROUND

Photo-polymerization is a process in which a monomer is converted to a polymer; the process is initiated by the absorption of visible or ultraviolet light. The light may be absorbed either directly by the reactant monomer (direct photo-polymerization) or by a photosensitizer that absorbs the light and then transfers energy to the monomer. The monomers then form a long chain or crosslinked network.

Some current dental restorative compositions rely on photo-copolymerization of resin monomers to form a stable, solid mass in an oral environment. However, to be practically useful, the polymerization must occur in a relatively short time frame. This need for rapid polymerization precludes the use of many materials and compositions that could perform well in an oral environment. As an example, styrene derivatives may perform satisfactorily in an oral environment, but current styrene derivative compositions require many tens of minutes or hours to polymerize, making such compositions unsuitable for dental restorative applications. Furthermore, current methacrylate derivative-based compositions, and their accompanying use instructions, may not produce satisfactory durability and esthetics over time. In addition to a short average service life, these compositions are subject to leaching of unreacted monomers and system degradation by hydrolysis of acids, bases, or enzymes.

In addition, although the polymerization rate of styrene may be improved through copolymerization with methacrylate monomers, the resulting composition may experience a significant composition drift as the conversion of monomers increases. Vinyl ester resins (VER), as an example, are copolymers of styrene and dimethacrylate monomers. At a high monomer conversion, more styrene is converted into polymer due to diffusion limitations. That is, the dimethacrylate monomers are more viscous than styrene, and thus diffuse more slowly than styrene to reach radicals as the polymerization progresses. This diffusion limitation becomes more obvious for VERs when styrene derivatives have two double bonds on a single monomer. The composition drift of copolymers at different monomer conversions may generate inconsistent physical and mechanical properties in the resulting polymers. FIG. 1A illustrates examples of such composition drift for two current co-polymer compositions, namely urethane dimethacrylate/triethylene glycol dimethacrylate (UDMA/TEGDMA) and bisphenol A glycidyl dimethacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA). In FIG. 1A, curve 1 represents a mixture of base monomer UDMA and diluent monomer TEGDMA, and curve 2 represents a mixture of base monomer Bis-GMA and diluent monomer TEGDMA. The base monomers have a viscosity of 6700 cP (centipoise) and the diluent monomer has a viscosity of about 20 cP. The feeding monomers have a 1/1 molar ratio. As the degree of vinyl conversion (DC) exceeds 60%, the amount of unpolymerized base monomer relative to the total increases sharply.

SUMMARY

Disclosed are compositions for enzymatically and hydrolytically stable dental applications, and methods for producing such compositions that can yield highly cross-linked, strong and durable polymers that form rapidly when exposed to light. The compositions may be used in restorative dentistry and can withstand the challenging conditions of the oral environment; however, the compositions may be useful in additional applications such as in medical devices, as coating and packing materials, as adhesives, as filters, as products requiring both strength and lightness (e.g., a tennis racket handle and frame, a golf club shaft, and automobile body parts and interior components), and in 3D printing.

In an aspect, disclosed are new and non-obvious compositions of resin monomers that enhance the polymerization rate of styrene derivatives over that achievable with current compositions and associated methods by the addition of methacrylate (MA) derivatives, and photo-initiators. Furthermore, with the herein disclosed compositions and methods, the molar ratios of styrene derivatives and MA derivatives in the monomer state can be retained in the polymeric state, and these ratios can be maintained throughout the process of polymerization regardless of the degree of monomer conversion. Furthermore, the viscosities of the monomers will not cause composition drift in the polymer. Finally, the diffusion limitation of copolymerization is overcome by using monomers containing carbamate functional groups or forming hydrogen bonds.

In an embodiment, the novel and non-obvious compositions of matter include two or more vinyl-containing monomer(s) and one or more initiators. The two or more vinyl-containing monomers undergo vinyl conversion to form a composition-controlled resin.

In an aspect, the two or more vinyl-containing monomer(s) are chosen from a group consisting of mixtures of methacrylate derivatives and styrene derivatives, and mixtures of acrylate derivatives and styrene derivatives; and the methacrylate and styrene moieties or the acrylate and styrene moieties are in a same monomer or different monomers.

In another aspect, one or more of the vinyl-containing monomer(s) have functional groups selected from a group consisting of one or more carbamate groups and/or derivatives; one or more urethane groups and/or derivatives; and one or more amine groups and/or derivatives.

In yet another aspect, the initiators are selected from a group consisting of photo-initiator(s) including camphorquinone or derivatives; a combination of camphorquinone or derivatives and amine(s), including ethyl-4-N, N-dimethyl-aminobenzonate; Phenylpropanedione or derivatives, including 1-phenyl-1,2-propanedione; and Bisacrylphosphine oxide or derivatives including bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (Irgacure 819), bis(2,6-dimethoxy benzoyl)-trimethylpentyl phosphine oxide and 1-hydroxycyclohexyl phenyl ketone. The photo-initiators may be used with/without diaryl iodonium derivatives, and with/without boryl radicals including tert-butylamine borane complex.

In still another aspect, the composition is used to achieve composition control of a forming polymer, wherein the mole fraction of acrylate/methacrylate moieties and styrene moieties in the forming polymer is determined preferably by the monomer reactivity (how fast the monomer is polymerized with itself in comparison with the other monomers. Preferably, copolymerization is faster than homo-polymerization) and composition of the feeding monomers rather than the viscosity of the feeding monomers,

In an embodiment, the composition of matter employs two or more vinyl-containing monomers that form hydrogen bond with each other. The monomers may be chosen from a group consisting of mixtures of methacrylate derivatives and styrene derivatives, and mixtures of acrylate derivatives and styrene derivatives; and the methacrylate and styrene moieties or the acrylate and styrene moieties are in a same monomer or different monomers.

In an aspect, the composition of matter employs one or more vinyl containing monomers having hydrogen donors and/or hydrogen acceptors and one or more vinyl containing monomers having hydrogen acceptors and/or hydrogen donors.

In another aspect, the composition of matter may comprise any mixture of vinyl containing monomers with at least one vinyl-containing monomer having hydrogen donors and at least another vinyl-containing monomer having hydrogen acceptors.

In another aspect, heat or increasing temperature is applied to reach high monomer conversion, control composition of copolymers and provide desired mechanical properties.

In still another aspect, the composition is used to achieve composition control of a forming polymer, wherein the mole fraction of acrylate/methacrylate derivatives and styrene derivatives in the forming polymer is determined preferably by the competing reactivity of monomers during polymerization and the composition of the feeding monomers rather than the viscosity of the feeding monomers. In an example, in a mixture of methacrylate (MA) derivatives and styrene (ST) derivatives, the MA tends to react with ST rather than the same monomer. This leads to alternating monomer units in the polymer chain. In contrast, composition drifted copolymerization generally results in polymer chains with randomly packed repeating units.

DESCRIPTION OF THE DRAWINGS

The detailed description refers to the following figures in which like numerals and symbols refer to like items, and in which:

FIG. 1A illustrates prior art compositions that undergo composition drift during photo-copolymerization;

FIG. 1B compares prior art compositions undergoing composition drift during polymerization with a composition-controlled polymerization according to the herein disclosed inventions;

FIGS. 2A and 2B illustrate examples of methacrylate (MA) derivatives that may be added to a composition containing styrene derivatives for use in dental compositions;

FIGS. 2C and 2D illustrate examples of methacrylate derivatives that may be used in a precursor composition to provide a composition controlled polymer;

FIG. 2E illustrates an example styrene derivative that may be added to a precursor composition to provide a composition controlled polymer;

FIG. 3 illustrates a precursor composition for dental applications that provides azeotropic photo-copolymerization of the MA derivatives and styrene derivatives of FIGS. 2A, 2B, and 2E;

FIG. 4 illustrates a comparison of a composition-controlled polymer and polymers formed by processes that undergo composition drift;

FIG. 5 illustrates the effects of changing light intensity on the degree of vinyl conversion (DC), when TEGDMA, UDMA, or BisGMA was copolymerized with TEG-DVBE at an equimolar composition;

FIG. 6 illustrates the effects of post-conversion heating of a polymer on glass transition temperature (Tg);

FIGS. 7A-7C illustrate the effects of azeotropic copolymerization compared to diffusion limited copolymerization; and

FIG. 8 illustrates the differences of polymer stress for composition-controlled and composition-drifted polymers.

DETAILED DESCRIPTION

With current compositions and associated methods, photo-polymerization of styrene derivatives occurs too slowly to be practically useful in dental applications. Disclosed herein are precursor compositions (resin monomer compositions) that include styrene derivatives and that reach satisfactory vinyl conversion within a time frame that is suitable for dental applications such as dental preventive and restorative applications, laminate veneers, dentures, denture repairing materials, inlays and onlays, fixed bridges, implants, resin reinforce cements, placement of ceramic restorations, and sealants. Also disclosed are methods for producing satisfactory resins for such dental applications.

The precursor compositions also may be used for products requiring both strength and lightness, such as golf club shafts and tennis rackets, automobile body parts and interior components.

With an ever-growing impetus to produce new, advanced functional materials, many synthetic approaches and conceptual designs have been developed, and opportunities are opened. A clinically implementable system that makes high performance functional polymeric materials on site, especially those with well-defined chemical structures, is appealing for various applications, including medical devices, coatings, packaging, electronic devices, solar cells, and the automobile industry. Photo-polymerization also may be used as a photographic or printing process, because polymerization only occurs in regions that have been exposed to light. Unreacted monomers can be removed from unexposed regions, leaving a relief polymeric image. Several forms of 3D printing, including layer-by-layer stereo lithography and two-photon absorption 3D photo-polymerization, also may use photo-copolymerization.

Polymers may be synthesized to have a broad array of physical, thermal, and chemical properties, and thus a need exists to tailor polymer materials synthesis to specific property sets. Commercial homopolymers are limited in their ability to be adjusted for simultaneous requirements, such as elasticity, impact strength, thermal transitions, and environmental resistance. This can be addressed to an extent with polymer blends, but compatibility and possible poor qualities of any of the blend components can affect the polymer. Copolymers provide a continuum of adjustment in the characteristics of the individual monomers, and are a flexible way to tailor polymer properties. An aspect of copolymerization that can affect the polymer's properties is termed composition drift or composition shift: a variation of the relative amounts of the monomer species and their packing sequence incorporated into the growing polymer chains during polymerization. Variations in viscosity of monomers may result in composition drift during polymerization. The synthesis process must incorporate controls to either reduce composition drift, or to tailor it to a profile that yields desired product finish properties. In copolymers, important properties like the heat distortion temperature, the decomposition temperature, and toughness depend not only on the molecular weight distribution, but also on the chemical composition distribution. Some polymers are intolerant of a composition drift as low as 3% to 5%. The degree of composition drift is directly affected by the reactivity ratios of each monomer in the precursor composition, and as monomer conversion increases, the copolymer composition will drift as the preferences for monomers change due to monomer reactivity ratios and the instantaneous concentration of each monomer. Composition drift in some degree will occur even the reactivity ratios for both monomers are equal to 1. This causes equal rates of consumption for copolymer formation and leads to random copolymerization. In this case, monomer viscosity takes control and leads the copolymerization more favorable to low viscosity monomers. The composition drift of copolymers at different monomer conversions may generate inconsistent optical, physical and mechanical properties in the resulting polymers. FIG. 1A illustrates examples of such composition drifts for two current co-polymer compositions, namely urethane dimethacrylate/triethylene glycol dimethacrylate (UDMA/TEGDMA) and bisphenol A glycidyl dimethacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA). In FIG. 1A, curve 1 represents a mixture of base monomer UDMA and diluent monomer TEGDMA, and curve 2 represents a mixture of base monomer Bis-GMA and diluent monomer TEGDMA. As the degree of vinyl conversion (DC) exceeds 60%, the amount of unpolymerized base monomer relative to the total increases sharply.

In addition, although the polymerization rate of styrene may be improved through copolymerization with methacrylate monomers, the resulting composition may experience significant composition drift as the conversion of monomers increases. Vinyl ester resins (VER), as an example, are copolymers of styrene and dimethacrylate monomers. At a high monomer conversion, more styrene is converted into polymer due to diffusion limitations. That is, the dimethacrylate monomers are more viscous than styrene, and thus diffuse more slowly than styrene to reach radicals as the polymerization progresses. This diffusion limitation becomes more obvious for VERs when styrene derivatives have two double bonds on a single monomer.

FIG. 1B illustrates composition drift for the two mixtures illustrated in FIG. 1A (curves 1 and 2) as well as composition stability for an example novel composition (curve 3) as disclosed herein. As can be seen in FIG. 1B, curve 3 represents the improved copolymerization, as disclosed herein, of styrene derivatives and methacrylate derivatives, showing an essentially constant ratio of the constituents from precursor to final copolymerization phases.

In an aspect, the precursor compositions include a styrene derivative to which is added a small amount of methacrylate (MA) derivatives. The methacrylate derivatives may contain urethane groups, carbamate groups, amide, and/or amine groups, preferably urethane groups as shown in FIGS. 2A and 2B, which illustrate two different forms of urethane dimethacrylate (UDMA). The UDMA may serve as a co-initiator in the herein disclosed photo-curable dental resins, and such UDMA containing resins should have a higher double bond conversion than would bisphenol A glycidyl dimethacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA) resins (see FIGS. 2C and 2D).

FIG. 2E illustrates an example styrene derivative that may be used with the methacrylate derivatives of FIGS. 2A and 2B. In particular, FIG. 2E illustrates triethyleneglycol divinylbenzyl ether (TEG-DVBE) with two styrene groups. However, other styrene derivatives that contain hydrogen donors or acceptors and form hydrogen bonds with methacrylate derivatives may be used.

In an aspect, the precursor composition may be comprised of a molar fraction of methacrylate derivatives, up to 80 percent of the total precursor composition (80 mole %), preferably 50 mole %. As can be seen in the example of FIG. 3, the precursor composition also may include photo-initiators in addition to the above-mentioned UDMA. In an embodiment, the photo-initiators may include quinone and amine initiator systems such as combinations of camphorquinone and ethyl-4,N, N-dimethyl-aminobenzonate.

The precursor composition may be cured by light irradiation, and preferably by visible light, or by heating. The polymerization may occur after the precursor composition infiltrates into pores of porous objects, wherein the porous objects include metal oxide, ceramic, chitosan, polysaccharide particles, metal, and wood.

Finally, the above monomers may be mixed with or without solvents or with or without fillers such as silica particles, carbon nanotubes, graphene, metal oxide particles, ceramic particles, chitosan, polysaccharide particles, and the particles are in nano-scale and micro-scale size.

By co-polymerizing with the methacrylate derivatives, the styrene derivatives may reach about a 60 percent or more degree of vinyl conversion (DC) within about one minute of light irradiation.

Further, the copolymerization of the precursor composition may follow an alternating copolymerization kinetics, and the precursor composition may have an azeotropic composition at the equimolar of styrene derivatives and methacrylate derivatives. Azeotropic composition means the mole ratio of styrene and methacrylate in the monomers is the same as that in the copolymer and is independent of the polymerization rate. This monomer reactivity-controlled process depends on the monomer reactivity ratios in the polymerization process. As a consequence, the repeating unit of copolymers is preferably styrene-alt-methacrylate. By selective control of the chemical structure of the feeding monomers, the desired performance of the light-cured dental resin is achieved; in particular, the feeding monomers are controlled to produce a dental resin having the desired polymerization shrinkage, hydrophilicity, hydrophobicity, and hydrogen bonding.

Furthermore, the dental resin formed using the monomers of FIGS. 2A, 2B, and 2E represents an improvement over current dimethacrylate (DMA) dental resins, which contain hydrolyzable ester groups. These ester groups may be split by acids, bases, and esterase present in the oral environment, leading to a short service life and leaching of unreacted monomers and system degradation products, e.g., bisphenol A (BPA). The herein disclosed new resin network at equimolar composition not only replaces 50% of the hydrolysable ester groups with hydrolytically stable ether-based monomers, but also the new resin network is formed with composition controlled polymers, which generate local heterogeneity due to the chemical structure difference between VBE and MA. The new resin network also may obstruct or limit big enzymes from contacting the ester groups through steric effects and thus prevent degradation of the ester groups. In addition, esterase enzymes from saliva and cariogenic bacteria have chemical selectivity to ester-based monomers; for example, acetylcholinesterase (CE) is more active on Bis-GMA, and pseudochloineesterase (PCE) is more active on TEGDMA, which also may be disturbed by the new chain structure (i.e., the new resin network) in the new compositions disclosed herein.

Still further, for MA derivatives containing urethane groups, carbamate groups, amide groups, and amine functional groups, preferable urethane groups serve an additional function as co-initiators, thereby reducing the amount of leachable photo-initiators needed in the precursor composition. Thus, the forming polymer is more biocompatible and safer for use in dental applications.

Finally, with certain of the herein disclosed precursor compositions, viscosity does not cause a deviation in the co-polymer composition (i.e., composition drift) as may happen in DMA-based co-polymer compositions. In addition, applicant provides precursor compositions and methods that deliver composition-controlled copolymerization for precursor compositions which generally show composition drift during polymerization. These methods including increase polymerization rate through enhancing light intensity or raising reaction temperature.

Following are examples of compositions and methods related to rapid photo-copolymerization that undergoes azeotropic copolymerization, composition-drift copolymerization and non-azeotropic, composition-controlled copolymerization. In these examples, the commercial monomers UDMA and ethoxylated bisphenol dimethacrylate (EBPADMA) were supplied by Esstech (Essington, Pa., USA) and were used as received. TEG-DVBE was synthesized and fully characterized by the applicant. The resin formations in the examples were activated either by 0.2 weight percent (wt %) of camphorquinone (CQ, Aldrich, Saint Louis, Mo., USA) and 0.8 wt % of ethyl 4-N,N-dimethylaminobenzoate (amine, Aldrich, Saint Louis, Mo., USA) or Irgacure 1819 for visible light photo-polymerization.

Example 0

Using solvents to encourage the formation of inter-species hydrogen bonds. In the preparation of monomer mixtures, the monomers and initiators were dissolves in hydrophobic solvents, e.g., methylene chloride. The solution was agitated using a magnetic stirrer for 30 minutes. Then, the solvent was removed by blowing dry air. One of the functions of the solvents was to break the intra-species hydrogen bonds formed by UDMA or BisGMA monomers, while encouraging the formation of inter-species hydrogen bonds, e.g., between UDMA and TEG-DVBE or BisGMA and TEG-DVBE.

Example 1

This example involves the use of FTIR spectroscopy, real-time Raman micro-spectroscopy, and one-hour (1H) NMR spectroscopy to evaluate the composition of monomer mixtures and their copolymers. The absorbance or scattering of vinyl groups on TEG-DVBE (a styrene-derivative) and UDMA (a methacrylate-derivative) were identified, separated, and quantified using FTIR spectroscopy and Raman spectroscopy. The vinyl groups on TEG-DVBE formed a stronger conjugation with their benzene rings than the vinyl groups on UDMA did with carboxyl groups. In addition, the di-substitution (methyl and carboxyl) of the β-carbon of methacrylates may cause the C═C stretching to shift to a lower energy. As a result, the vinyl groups on TEG-DVBE and UDMA exhibited peaks at approximately 1629 cm⁻¹ and 1638 cm⁻¹, respectively, in both FTIR and Raman spectra. The separation and quantification of the C═C peaks of these two monomers was realized through peak-fitting using mathematical models developed for FTIR and Raman spectroscopy. In the wave number ranging from 1580 cm⁻¹ and 1660 cm⁻¹, four peaks were identified. Besides the absorption of C═C stretching of vinyl groups, the C═C stretching of the benzene ring from TEG-DVBE (1612 cm⁻¹) and N—H bending from UDMA (1623 cm⁻¹) were observed, respectively.

Example 2

The mixture of TEG-DVBE and UDMA monomers at an azeotropic composition (i.e., 1/1 mole ratio) had higher reactivity toward free-radical photo-polymerization than ethoxylated bisphenol A dimethacrylate (EBPADMA) and approximately the same reactivity as that of UDMA. For the degree of vinyl conversion (DC) of EBPADMA, UDMA and UDMA/TEG-DVBE mixtures immediately after light irradiation (20 seconds, 40 seconds, or 60 seconds, using Smartlite® Max at 1600 mW/cm²), mixtures of CQ and 4E (0.2 wt % and 0.8 wt %, respectively) were used as an initiator. Using the same initiators and curing light, the DC of monomer mixtures (UDMA/TEG-DVBE/=1/3) reached 79% immediately after 40 seconds of light irradiation. Increasing the amount of UDMA makes the polymerization rate even faster. At a 1/1 mole ratio, UDMA/TEG-DVBE initiated by CQ/4E was found to be the fastest system among the three systems evaluated with different initiators and monomer mixtures.

Example 3

As noted herein, and as described in this example 3, azeotropic composition in copolymers means that the fractions (mole ratio) of the starting monomers are the same as their fractions in the copolymers, and this mole ratio is constant throughout the copolymerization process. As an example, alternating copolymers of styrene and methyl methacrylate (MMA) have an azeotropic composition, 1/1 by mole. Three methods, FTIR-ATR, confocal Raman micro-spectroscopy, and NMR were used to confirm that equimolar UDMA/TEG-DVBE was an azeotropic composition when CQ/4E was used as an initiator, but not when Irgacure 819 was used as an initiator. The vinyl groups on TEG-DVBE (peak at 1630 cm⁻¹) and UDMA (peak at 1639 cm⁻¹) were identified and separated by both FTIR and Raman spectroscopy, and the intensity ratio of these peaks was proportional to the mole ratio of the two corresponding monomers. Kinetic studies using confocal Raman micro-spectroscopy confirmed that the ratio of peak intensity of UDMA/TEG-DVBE did not change, no matter how fast the photo-copolymerization was, nor how high the DC was. The polymerization rate was controlled through the intensity of irradiation light to obtain fast (150 mW/cm² for 20 seconds) and slow (4 mW/cm² for 5 seconds) reactions. In addition, NMR also confirmed that the mole ratio of monomers was constant (1/1) at different DCs, from 5% to 60%. Using the same NMR method, UDMA (viscosity 7000 cP (centipoise)) was found to have a reduced fraction at high DC in copolymers with TEGDMA, due to viscosity effects. Even though TEG-DVBE had a similarly low viscosity (29 cP) as TEGDMA (12 cP), applicant did not observe any viscosity effects throughout all of the reaction conditions that were evaluated.

Example 4

Diffusion limitations lead to less monomer conversion (lower DC) of high viscosity monomers when no carbamate functional groups are in the monomers. The copolymerization of a mixture of EBPADMA with TEG-DVBE, 1/1 by mole, initiated by camphor quinone and amine showed that more TEG-DVBE was converted into polymer, and the mole fraction of TEG-DVBE-polymer was higher than polymerized EBPADMA at high monomer conversion. The mixture of monomers and initiators was irradiated for 20 seconds with a curing gun at 400 mW/cm². The DC of each monomer during copolymerization was monitored by real-time FTIR.

Example 5

Diffusion limitations lead to less monomer conversion of high viscosity monomers when no carbamate functional groups are in the monomer. The copolymerization of mixture of EBPADMA with TEG-DVBE, 1/1 by mole, initiated by 1819 showed that more TEG-DVBE was converted into polymer, and the mole fraction of TEG-DVBE-polymer was higher than polymerized EBPADMA at a high monomer conversion. The mixture of monomer and initiators was irradiated for 20 seconds with a curing gun at 400 mW/cm². The DC of each monomer during copolymerization was monitored by real-time FTIR.

Example 6

Diffusion limitations lead to more monomer conversion of high viscosity monomer when carbamate functional groups are in the high viscosity monomer. The copolymerization of a mixture of UDMA with TEG-DVBE, 1/1 by mole, initiated by 1819 showed that more UDMA was converted into polymer, and the mole fraction of UDMA-polymer was higher than polymerized TEG-DVBE at high monomer conversion. The mixture of monomer and initiators were irradiated for 20 seconds with a curing gun at 400 mW/cm².

Example 7

The copolymer of UDMA/TEG-DVBE generated less stress than the copolymer of Bis-GMA/TEGDMA at the same DC when initiated by CQ/amine.

Example 8

A composite was made by resin (25% by mass) and silica particles as fillers (75% by mass). The resin was a mixture of UDMA/TEG-DVBE 3/1 (by mole) and CQ/4E. The mixture was cured by light irradiation, and the cured composite had the same rigidity as composites made of Bis-GMA/TEGDMA but had significantly high flexural strength and toughness.

Example 9

The degree of vinyl conversion (DC) of the mixture of UDMA/TEG-DVBE (1/1 by mole) with CQ/amine as initiator was approximately 86% after 1 minute of light irradiation. The DC was further increased by heat. The DC was approximately 96% after 24 hours at 60 degrees centigrade; and the DC reached >99% after 0.5 hours at 200 degrees centigrade.

Example 10

This example describes photo-polymerization methods. Monomer mixtures were sandwiched between two Mylar films (10 μL, for FTIR-ATR measurement) or sealed in capillary glass tubes (Vitrocom, Mt. Lks. N.J., USA; 0.40×4.0 I.D., for real-time Raman micro-spectroscopy evaluation) and photo-cured using a handheld dental curing light (SmartLite max LED curing light, model: 644050, Dentsply International, Milford, Del., USA). The intensity of light irradiation was adjusted through the distance of light to samples.

Example 11

This example determined degree of conversion (DC) using FTIR-ATR and peak fitting methods. DC was evaluated immediately after curing using a Thermo Nicolet Nexus 670 FT-IR spectrometer (Thermo Scientific, Madison, Wis., USA) with a KBr beamsplitter, an MCT/A detector and an attenuated total reflectance (ATR) accessory. The areas of absorption peaks of the vinyl group of TEG-DVBE at 1629 cm⁻¹, and the methacrylate groups of UDMA at 1638 cm⁻¹ were integrated, and the DC was calculated using the aromatic group of TEG-DVBE at 1612 cm⁻¹ or the amide group of UDMA at 1537 cm⁻¹ as an internal standard. Peaks were resolved with the assistance of the curve fitting program Fityk (version 0.9.8). In order to correct potential discrepancies, a standard curve was produced by plotting varied resin composition ratio values analyzed by NMR spectroscopy against the values obtained through FTIR peak fitting. The phenyl absorbance at 1612 cm⁻¹ was the internal standard for TEG-DVBE homo-polymers. DC was calculated according to the following equation: DC=(A1/A0−A1′/A0′)/(A1/A0) 100%, where A1/A0 and A1′/A0′ stand for the peak-area-ratio of vinyl-of-interest and internal standard before and after polymerization, respectively. The vinyl-of-interest may be vinyl groups from TEG-DVBE, UDMA, or both.

Example 12

Sol-gel experiment. Resin specimens were placed in a stainless steel mold (13 mm in diameter and 1 mm in thickness) and then cured for different time scales (10 seconds, 20 seconds and 60 seconds) with a Triad 2000 visible light curing unit (Dentsply, York, Pa., USA) fitted with a tungsten halogen light bulb (75 W and 120 V, 43 mW/cm²). The samples were then weighed and their DCs were determined by FITR-ATR immediately after the curing. In a pre-weighed vial, each sample was extracted twice using 5 mL deuterated methylene chloride (CDCl3) containing 0.01 wt % butylated hydroxytoluene (Aldrich, Saint Louis, Mo., USA) via continuous shaking for 48 hours. The solution (sol) fractions from these two extractions were combined and concentrated via rotary evaporation under reduced pressure until no further changes in weight were observed. 1H NMR (Bruker 600 MHz) was conducted for each sol fraction sample to determine the monomer ratio. The remaining gel fraction was collected and dried via in-house vacuum to yield a constant weight, and the DC was measured by FTIR-ATR.

Example 13

Real-time Raman micro-spectroscopy: method description, peak fitting method, and real-time DC evaluation. Raman spectra were acquired from dried residues using a Renishaw S1000 micro-Raman spectrometer (Renishaw, Gloucestershire, UK) consisting of a Leica DMLM microscope coupled to a 250 mm focal length imaging spectrograph with a proprietary deep depletion, thermoelectrically cooled (70 degrees centigrade) charge-coupled device. For this work, a 632.8 nm helium-neon laser (Model 1144P, JDS Uniphase, Milpitas, Calif.), holographically ruled 1800 grooves mm⁻¹ grating, and 20× objective (Leica N PLAN) were used. The excitation laser was focused to a line approximately 50 μm long at the sample position and aligned to the spectrograph entrance slit to maximize throughput. The line focus was utilized to reduce laser power density at the sample. Laser power measured at the sample position was approximately 12 mW. Depending on the desired spectral range, data was acquired using a static grating position covering the Raman shift range from 1275 cm⁻¹ to 1790 cm⁻¹ (577 data points) or a grating step scan mode covering the Raman shift range from 500 cm−1 to 1800 cm⁻¹ (1369 data points). Integrations time was typically 1 second/pixel. Spectral resolution was approximately 3 cm⁻¹. To further minimize any unintended impacts of laser illumination on the photo-polymerization the samples used in the kinetic studies were slowly translated laterally throughout data acquisition. This was done using the motorized microscope translation stage and Raman mapping capabilities in the spectrometer control software (WiRE 3.1, Renishaw, Gloucestershire, UK).

Estimation of the degree of conversion of the monomers was accomplished using a direct classical least squares (CLS) multivariate regression approach. Pure spectra of each monomer were acquired by placing the neat materials in the same vessels as used for the photo-polymerization kinetic studies and collecting spectra with equivalent excitation laser power and integration time to provide spectra that were quantitative relative to one another. The spectral range was restricted to a narrow spectral range from 1625 cm⁻¹ to 1660 cm⁻¹, which corresponds to the stretching modes of the terminal vinyl groups on each monomer. This narrow range was necessary because of band intensity changes and small band shifts observed for many of the vibrational modes as a consequence of the polymerization. Blending of the monomers appeared to introduce small peak shifts 0.5 cm⁻¹) in the vinyl stretching modes that were correlated with the mixture composition. The pure spectra were shifted slightly prior to application of the CLS method in order to minimize the fit residuals. In addition to the two monomer pure spectra, a constant offset was fit in the CLS model in order to correct for baseline variations that arose during the experiments. A simple constant was deemed adequate because the CLS models were fit over a very narrow region of 35 cm⁻¹, which corresponds to a spectral band of only 1.75 nm, and fluorescent background interferences generally have much broader spectral profiles. The CLS scores are the contribution of each component of a linear combination of the pure spectrum in a least squares fit of the sample spectra. This is essentially a rigid peak fitting using an arbitrary experimentally measured peak function with a single parameter that corresponds to intensity. The pure spectra were acquired under identical instrumental conditions and thus the CLS scores were assumed to correspond directly to the relative composition of the monomer mixture before and during the polymerization. To estimate degree of conversion of each monomer, the CLS scores for each polymerization data set were normalized by the average score for the given component from an initial data set (typically ten or more spectra) acquired prior to photo initiation.

Example 14

Rapid Photo-polymerization: One of the synergetic effects of the model monomers is the significant improvement of polymerization rate of the styrene-derivative, TEG-DVBE, by adding UDMA. Free radical homo-polymerization of styrene is relatively slow in comparison with methacrylate due to stabilization of free radicals through resonance with styrene's benzene ring. Without modifying the chemical structure of the monomer or inventing new initiators, copolymerization is one of the most efficient ways to accelerate polymer chain propagation because the rate of copolymerization is strongly affected by the competition of monomer reactivity ratios (r1 and r2), which overcomes the drawback of free-radical stabilization in homo-polymerization of TEG-DVBE. Although substantial work has been done to improve the polymerization rate of styrenic monomer in vinyl ester resins (VERs) (Rey et al. Macromolecules 2000, 33, 6780, and Scott et al. Macromolecules 2003, 36, 6066), the polymerization rate and low degree of vinyl conversion are still limiting factors for VERs to be used clinically in dental adhesives and dental composites. This experiment demonstrates the viability of using model monomers in dental clinics by reaching DC above 70% with 20 seconds of light irradiation. The DCs of TEG-DVBE, UDMA, and the equimolar mixture of TEG-DVBE and UDMA immediately after light irradiation (light intensity at 1600 mW/cm²) for 20 seconds, 40 seconds, and 60 seconds were determined. The resulting low DC indicates that camphorquinone/ethyl 4-N, N-dimethylaminobenzoate (CQ/amine) are not efficient initiators for TEG-DVBE homo-polymerization. This initiator combination is however very effective on UDMA homo-polymer and the copolymer: their DCs reaching approximately 90% in 20 seconds.

Example 15

Another noteworthy feature is the azeotropic composition at equimolar TEG-DVBE and UDMA when CQ/amine are used as initiators. Azeotropic compositions in copolymers mean that the mole fractions of the feed monomers are retained in the polymer and are constant throughout the polymerization process. FTIR also revealed that the DC of TEG-DVBE and UDMA in the above equimolar copolymers was the same, approximately 90%. The composition of copolymers was further evaluated by the sol-gel experiment. To extract enough leachable materials, the light intensity was reduced to mW/cm², and low DC copolymers were obtained. The progress of photo-polymerization was controlled by varying the time of light irradiation. Based on the peak-area analysis of the absorbance of C═C stretching in FTIR spectra and integration of 1H NMR signals associated with protons on C═C, the styrene-vinyl groups and methacrylate-vinyl groups had the same mole fraction in both gels and solubles. This suggests that the equimolar composition of the feed monomers was maintained in these three polymerization stages from DC=5% to DC=62%.

Example 16

The azeotropic composition confirmed by real-time Raman spectroscopy: Real-time Raman micro-spectroscopy further confirmed that the equimolar composition was constant over time during photo-polymerization and was independent of the polymerization rate, which was controlled through light intensity and irradiation time. To achieve a step-wise polymerization, specimens were exposed to light at 4 mW/cm² for 5 seconds up to a total of four exposures. The multivariate CLS method standardized using pure monomer spectra was used to estimate unpolymerized monomer composition in the samples using the C═C stretching bands of TEG-DVBE and UDMA. CLS scores for each specimen were normalized to 100 for the pre-polymerized monomer mixtures. As the vinyl groups converted to polymers, the associated C═C band intensity decreased, and the DC increased accordingly. At each light irradiation, the intensity dropped immediately, which was followed by further decrease at a much slower rate, until the next irradiation. During the full time range (10 minutes) of this set of experiments, DC reached approximately 20%, and the mole ratio of TEG-DVBE/UDMA remained 1/1. A faster photo-polymerization took place when the sample was irradiated at 150 mW/cm² for 20 seconds. The DC of this specimen achieved approximately 55% immediately after light irradiation; after 1 hour, the DC was approximately 65%; after 1 day, it was approximately 72%. During the course of this set of experiments, the mole ratio of TEG-DVBE and UDMA was always 1/1.

Example 17

The azeotropic composition predicted by monomer reactivity ratios: Monomer reactivity ratios were evaluated to understand the kinetics behind the azeotropic composition at equimolar composition. The polymer composition (F) was determined by Raman micro-spectroscopy according to the CLS score ratios of TEG-DVBE and UDMA at low DCs (1-3%). A classic instantaneous copolymerization equation for non-cross-linking polymers was used to compare F with the monomer feed composition (f, mole fraction) based on an assumption that at such low DCs, the two vinyl groups in one molecule act independently without interfering with each other.

The feed ratios of monomers may not always determine the compositions of the final material. Feeds with a molar ratio UDMA/TEG-DVBE>0.5 are expected to produce resin networks depleted in their UDMA content relative to the feeds, and UDMA/TEG-DVBE<0.5 produce networks enriched in UDMA. The composition data were fit to an equation with a nonlinear least-squares (NLLS) optimization after van Herk. The monomer reactivity ratios, rUDMA and rTEG-DVBE, are 0.64±0.11 and 0.55±0.12, respectively. They are slightly, but statistically significantly higher than the reactivity ratios of styrene and methyl methacrylate, r1≈r2≈0.5. These reactivity ratios suggest a polymerization mechanism somewhat biased towards cross-propagation and alternating sequences, characteristic of styrenic-methacrylic copolymer systems.

Example 18

The effects of viscosity and monomer chemistry on composition control: Both of the sol-gel experiments and kinetic studies suggest the copolymerization of TEG-DVBE and UDMA is a monomer-chemistry-controlled process. The viscosity of monomer shows no consequential role during the polymer chain propagation, considering that the viscosity of UDMA (6.631±0.100 Pas (Pascal seconds)) is approximately 240 times higher than that of TEG-DVBE (0.029±0.001 Pas). In contrast, copolymerization of UDMA and triethylene glycol dimethacrylate (viscosity=0.050 Pas) showed significantly composition drift when DC was above 20% because the low viscosity monomers diffused faster in resin networks than the base monomers and reached the propagating chain quicker, thus more of them were converted into polymers at high DCs. Although the exact mechanism that leads to such rapid photo-polymerization and well-controlled azeotropic composition is yet to be defined, UDMA has dual roles: monomer and co-initiator when initiated by CQ/amine. The carbamate functional group in UDMA may form a free radical on a methylene group adjacent to its N—H groups. This may be achieved via electron transfer from the light-excited CQ. Experimentally, the photo-polymerization rate of UDMA initiated by CQ alone was similar to that by CQ/amine, and the photo-bleaching rate of CQ in UDMA also showed minimal differences with/without amine.

Besides compositions of UDMA and TEG-DVBE, other monomer compositions may be used in a composition-controlled polymerization process. These additional monomer compositions may employ a new mechanism that explains how to reach composition-controlled copolymerization and how the structure change occurs by composition change in the polymer, and the consequential mechanical property changes.

One such new mechanism is hydrogen bonding between monomers, which maintains the composition during photo-polymerization. Hydrogen bonding may be important for achieving azeotropic (composition-controlled is a more general term than azeotropic) copolymerization. For example, UDMA/TEG-DVBE forms hydrogen bonding. The hydrogen bonding maintains these two monomers in a preferable composition during photopolymerization. Such preferable composition may be disturbed by increased reaction temperature and slow down the polymerization. For the UDMA/TEG-DVBE copolymers with controlled-composition or drifted-composition, their mechanical properties in terms of elastic modulus and glass transition temperature are significantly different.

The hydrogen bonding mechanism reveals new monomer compositions and polymerization methods. For example, BisGMA/TEG-DVBE that otherwise would not form a composition-controlled copolymer, may be polymerized with constant monomer composition when the polymerization rate is sufficiently high.

The hydrogen bonding not only maintains composition control in a polymer, it also may increase the polymerization rate and final degree of vinyl conversion (DC). In comparison to monomer combinations that do not form hydrogen bonding, the H-bonded monomers may reach a higher DC at a high polymerization rate. In contrast, without hydrogen-bonding, polymerization rate increases makes the final DC lower.

In an embodiment, rapid, non-azeotropic but composition-controlled copolymerization of BisGMA/TEG-DVBE was achieved by high-speed photo-polymerization with high light intensity. Examples include comparison of composition-drifted copolymerization of BisGMA/TEG-DVBE at low light intensity, and composition-controlled copolymerization at high light intensity.

Composition-controlled copolymerization also may be achieved by using monomers that do not form hydrogen-bonds, but the increase of polymerization rate causes a decrease in final DC.

Following are examples of compositions and methods related to rapid non-azeotropic composition controlled photo-copolymerization:

General description: Viscosity differences in monomer mixtures; base monomer vs diluent monomer. By applying hydrogen bonding, monomer mixtures that comprise monomers with significant viscosity differences may be used to achieve composition-controlled copolymerization, thereby overcoming the diffusion limitation and composition-drift during copolymerization. Composition drift can lead to unwanted and/or uncontrolled structure changes during polymerization, with consequent effects on the mechanical properties of the polymer. By matching monomer viscosity in a monomer mixture, composition-controlled copolymerization may achieved. However, an increase polymerization rate will decrease the degree of vinyl conversion (DC), and DC above 90% cannot be reached. Applicant discovered that by applying hydrogen-bonding among monomers in their mixed state, rapid, high-DC and composition-controlled copolymerization could be achieved. The degree of vinyl conversion (DC) increased when polymerization rate increased, and a DC above 90% was reached.

Example 19

Materials and preparation of monomer mixtures. Triethylene glycol-divinylbenzyl ether (TEG-DVBE) was synthesized and fully characterized by applicant. Urethane dimethacrylate (UDMA), bisphenol A glycidyl methacrylate (BisGMA), Ethoxylated bisphenol A dimethacrylate (EBPADMA), triethylene glycol dimethacrylate (TEGDMA) were obtained from Esstech (Essington, Pa., USA), and were used as received. Styrene was purchased from Sigma-Aldrich, and was used as received. Resin polymerization was initiated by Irgacure 819 provided by Ciba, using visible light photo-polymerization.

The above monomers were prepared by choosing and mixing two monomers in equimolar amount with 1 wt % of Irgacure 819 as the photo-initiator. the mixture was subjected to ultrasound to provide a clear transparent liquid. The monomer mixtures were sealed in glass tubes (2 mm×2 mm×10 mm) for Raman spectroscopy evaluation. The monomer mixtures were photo-cured using a 390 nm UV LED at a variety of light irradiation intensity (10-1000 mW/cm²).

Example 20

Raman spectroscopy to evaluate degree of vinyl conversion and composition simultaneously: Raman spectroscopy enables the kinetics study and composition analysis of monomer mixtures during copolymerization, through real-time monitoring of monomer reactive double bond peak intensity. This setup can be very conveniently employed to study copolymerization of systems with well-resolved monomer reactive groups, such as a typical Vinyl Ester Resin (VER) composite, or a base-diluent monomer mixture system. Raman spectroscopy showed Raman shifts between 1590 and 1670 cm⁻¹ for six vinyl monomers: BisGMA, UDMA, TEGDMA, EBPADMA, TEG-DVBE and styrene (for respective structures of the monomers, see FIGS. 2A-2E). The same Raman spectroscopy also was useful for studying copolymerization of vinyl ester resins (VER). Vinyl groups from TEG-DVBE and styrene formed a stronger conjugation with their adjacent benzene rings, and thus exhibited higher energy at the stretching mode, compared to methacrylate vinyl groups from BisGMA, UDMA, TEGDMA and EBPADMA. As a result, styrene-vinyl and methacrylate-vinyl groups can be attributed to peaks at 1629 cm⁻¹ and 1638 cm⁻¹ in Raman spectra, respectively, with good accuracy. Moreover, the iconic stretching of benzene rings in aromatic monomers such as BisGMA, EBPADMA, TEG-DVBE and styrene were observed in the range between 1600 and 1615 cm⁻¹. Due to the well resolved styrene-vinyl and dimethacrylate peaks in Raman spectroscopy, the monomer compositions of the copolymerization reactions composed of these two groups of widely employed monomers can be readily monitored by comparing the intensity of the two peaks relative to their initial intensity (e.g., degree of vinyl conversion). Kinetics results can be derived from peak-fitting of real-time monomer composition Raman data.

Example 21

Azeotropic and composition-controlled vs composition-drift copolymerization at different light intensity (10 mW/cm² and 500 mW/cm²). In this example, two equimolar monomer mixtures, UDMA/TEG-DVBE and BisGMA/styrene, were photo-polymerized and initiated by different light intensity, e.g., 10 mW/cm² and 500 mW/cm². The monomer conversion during the polymerization was monitored by Raman spectroscopy. UMDMA/TEG-DVBE underwent composition-controlled copolymerization (FIG. 7A), while BisGMA/styrene experienced composition drift copolymerization (FIG. 7B). With the BisGMA/styrene composition, more styrene monomers were converted into polymers than BisGMA monomers; thus the equimolar composition in the feeding monomer mixture was not maintained in the polymer network, which had more poly-styrene than poly-BisGMA.

Example 22

Hydrogen bonding in monomer mixtures. Hydrogen bonding is an inter- or intra-molecular interaction between a hydrogen donor and a hydrogen acceptor. The monomers BisGMA and UDMA have both hydrogen donors (OH groups and NH groups) and hydrogen acceptors (—O— in the ether groups and ester groups, C═O in ester groups and carbamate groups—see FIGS. 2A-2C), while the monomers TEG-DVBE, TEGDMA, and EBPADMA only have hydrogen acceptors (see FIGS. 2D and 2E). Styrene has neither hydrogen donors nor hydrogen acceptors, and thus styrene cannot form hydrogen bonds with any of the other monomers. However, certain styrene derivatives, such as TEG-DVBE, do have hydrogen acceptors, and thus can form hydrogen bonds with hydrogen donor monomers. TEG-DVBE, TEGDMA and EBPADMA cannot form hydrogen-bonds with each other. BisGMA and UDMA can form hydrogen-bonds with themselves or with TEG-DVBE, TEGDMA and EBPADMA.

Example 23

Viscosity: The viscosity of the above six monomers are: styrene (0.8 cP (centipoise; 1 cP=1 mPa s))<TEGDAM TEG-DVBE (20 cP)<EBPADMA (700 cP)<UDMA (3000 cP)<<BisGMA (130000 cP).

Example 24

Composition-controlled copolymerization with/without hydrogen bonding. This example shows the difference between composition-controlled copolymerization with and without hydrogen bonding. Composition-controlled copolymerization may be achieved without hydrogen bonding by adjusting the viscosity of the monomers. TEGDMA and TEG-DVBE have the same viscosity, but they cannot form a polymer through hydrogen bonding since neither monomer has any hydrogen donors. When mixed together, these two monomers were converted into polymers at the same rate and thus maintained an equimolar composition. However, when the light intensity was increased from 100 mW/cm² to 1000 mW/cm², the final degree of vinyl conversion (DC) of the copolymers was reduced from 80% to below 60%. In comparison, all mixtures of UDMA/TEG-DVBE and BisGMA/TEG-DVBE can form hydrogen bonds and achieve composition-controlled copolymerization. Due to the significant difference in viscosity as suggested in BisGMA/styrene mixtures, without hydrogen bonding, the composition drifted during polymerization. In addition, when the light intensity was increased from 10 mW/cm² to 1000 mW/cm², the final DC increased from 50% to 70% and 82%, respectively, for the BisGMA/TEG-DVBE and UDMA/TEG-DVBE. Thus, the downward trend in final DC was reversed when hydrogen bonds form.

Example 25

Adjust copolymer composition through light intensity. The equimolar mixture of BisGMA/TEG-DVBE may be copolymerized either through composition-controlled or composition-drifted processes through varying the intensity of the curing light (FIG. 7C) At low light intensity, e.g., 10 mW/cm², the monomer mixture undergoes composition-drifted copolymerization, and because the polymerization was slow, the impact of diffusion limitation still dominated. In a slow reaction, low viscosity monomers had sufficient time to reach the reactive sites and be converted into the polymer chains, while the movement of high viscosity monomers were limited due to the hindered diffusion within the polymer network. Based on Stokes-Einstein equation, the diffusion coefficient is inversely proportional to the viscosity. When the light intensity was increased to 1000 mW/cm², composition-controlled copolymerization takes place due to hydrogen bonding holding monomers together in organized forms (defined as monomer preorganization before polymerization).

Example 26

Adjust copolymer composition through temperature variation. An equimolar mixture of UDMA/TEG-DVBE was light cured to reach DC of 83.6±0.8%. The polymers then were subjected to two different temperature treatments. One is baked at 60 degrees C. for 5760 minutes, and the other was baked at 200 degrees C. for 30 minutes. At the end of the treatments, both polymers reached approximately 99% DC. The polymers were examined by dynamic mechanical analysis (DMA) to determine glass transition temperature (Tg—Tg is defined as the temperature where a polymer change from a solid-like material to a liquid-like material) based on the change of loss modulus and storage modulus as a function of temperature. The Tg experiment suggests polymers treated at 200 degrees C. are more uniform in structure and have a higher Tg than polymers treated at 60 degrees C. At both temperatures, the hydrogen bonds were broken. Because the monomers were rapidly converted at 200 degrees C., the composition likely was maintained from monomers to polymer. However, at 60 degrees C. for 4 days, the monomers, oligomers, and other unpolymerized component may have diffused within the existing polymer network, which resulted in a more diverse polymer network and a lower Tg. See FIG. 6.

Example 27

Comparing structure and mechanical properties between copolymers that are cured via composition-controlled or composition drift process. In addition to the above DMA evaluation on Tg and the polymer network, the elastic modulus evaluation suggests that the high temperature, short time treatment produced a more rigid polymer. The elastic moduli were 2.07±0.05 and 2.47±0.05 for polymers treated at 60 degrees C. and 200 degrees C., respectively.

Example 28

Applying composition-controlled copolymerization may reduce the polymerization stress. FIG. 8 shows the stress development of three resin mixtures: BisGMA/TEGDMA, UDMA/TEGDMA and UDMA/TEG-DVBE. The first two resin mixtures underwent a composition drift copolymerization, while the third one was copolymerized in a controlled composition. At the same DC (approx. 65%), the polymerization stress was 2.3, 2.9 and 1.1. respectively. The composition-controlled copolymerization produced significantly less stress than the others, which may due to a modest polymerization acceleration during the light irradiation process. 

I claim:
 1. A composition of matter, comprising: two or more vinyl-containing monomer(s); a hydrophobic solvent operable to inhibit intra-species hydrogen bonding; and one or more initiators, wherein the monomers form inter-species hydrogen bonds and undergo vinyl conversion to form a composition-controlled resin.
 2. The composition of matter of claim 1, wherein: the two or more vinyl-containing monomer(s) are chosen from a group consisting of mixtures of methacrylate derivatives and styrene derivatives, and mixtures of acrylate derivatives and styrene derivatives; and the monomers containing methacrylate derivatives or acrylate derivatives form hydrogen bonding with the monomers containing styrene derivatives.
 3. The composition of matter of claim 1, wherein the initiators are selected from a group consisting of: photo-initiator(s) including camphorquinone or derivatives, a combination of camphorquinone or derivatives and amine(s), including ethyl-4-N, N-dimethyl-aminobenzonate; or Phenylpropanedione or derivatives, including 1-phenyl-1,2-propanedione; or Bisacrylphosphine oxide or derivatives, including bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (Irgacure 819), bis(2,6-dimethoxy benzoyl)-trimethylpentyl phosphine oxide, and 1-hydroxycyclohexyl phenyl ketone, wherein the initiators may be used: with/without diaryl iodonium derivatives, and with/without boryl radicals including tert-butylamine borane complex.
 4. The composition of matter in claim 1, wherein the composition is used to achieve composition control of a forming polymer, wherein the mole fraction of acrylate/methacrylate derivatives and styrene derivatives in the forming polymer is determined preferably by the competing reactivity of monomers during polymerization and composition of the feeding monomers rather than the viscosity of the feeding monomers.
 5. The composition of matter in claim 1, wherein the composition control of the forming polymer is realized by enhancing polymerization rate through varying reaction conditions including increasing light intensity for photo-polymerization and increasing reaction temperatures.
 6. The composition of matter of claim 1, wherein the composition is used as dental materials that are used with or without fillers as restorative materials, laminate veneers, denture, denture repairing materials, dental adhesives, resin reinforce cements, placement of ceramic restorations, and sealants.
 7. The composition of matter of claim 1, wherein the composition is used in additive manufacturing with or without fillers to control the polymer composition, materials structure and mechanical properties.
 8. The composition of matter of claim 1, wherein the composition is used to make thermal-set resins that are stable against environmental challenges consisting of hydrolysis, corrosion, enzymatic degradation, and bacterial challenges.
 9. The composition of matter of claim 1, wherein the composition is used to make polymers as packaging materials, coating materials and adhesives.
 10. A composition of matter made by polymerizing the composition of claim 1 with or without fillers using methods comprising light irradiation and/or heating.
 11. The composition of matter of claim 10, wherein the fillers are selected from a group consisting of: carbon nanotubes, graphene, metal oxide particles, ceramic particles, chitosan, polysaccharide particles, and the particles are in nano-scale and micro-scale.
 12. The composition of matter of claim 11, wherein the composition is used as dental materials, restorative materials, laminate veneers, denture, denture repairing materials, dental adhesives, inlays and onlays, fixed bridges, implants, resin reinforce cements, placement of ceramic restorations, and sealants.
 13. The composition of claim 11, wherein the composition is used in articles of manufacture comprising: sporting articles comprising golf club shafts and tennis racket frames; and automobile body parts and interior components.
 14. The composition of claim 11, wherein the composition is used in 3D printing.
 15. A composition of matter made by polymerizing the composition of claim 1 after the composition infiltrates into pores of porous objects using methods comprising light irradiation and/or heating.
 16. The composition of matter of claim 15, wherein the porous objects are selected from a group consisting of: metal oxide, ceramic, chitosan, polysaccharide particles, metal, and wood.
 17. The composition of matter of claim 15, wherein the compositions are used as dental materials, restorative materials, laminate veneers, denture, denture repairing materials, dental adhesives, inlays and onlays, fixed bridges, implants, resin reinforce cements, placement of ceramic restorations, and sealants.
 18. A composition of matter made by polymerizing the composition of claim 1 to make vinyl-free polymers, polymers with no polymerizable vinyl groups, using methods comprising light irradiation and/or heating.
 19. The composition of matter of claim 18, wherein the compositions are used independently or as a component in sporting articles comprising golf club shafts and tennis racket frames; automobile body parts and interior components; carbon fibers, medical devices, electronic devices, and solar cells.
 21. A composition of matter, comprising: two or more vinyl-containing monomer(s); and one or more initiators, wherein the monomers do not form hydrogen bonds and the monomers undergo vinyl conversion to form a composition-controlled resin.
 22. The composition of matter of claim 21, wherein: the two or more vinyl-containing monomer(s) are chosen from a group consisting of mixtures of methacrylate derivatives and styrene derivatives, and mixtures of acrylate derivatives and styrene derivatives; and the monomers containing methacrylate moieties or acrylate moieties don't form hydrogen bonding with the monomers containing styrene moieties. 